Work vehicles such as a hydraulic excavator, a bulldozer, a wheel loader, and the like have an exhaust gas treatment device. For example, a diesel particulate filter device (DPF), a diesel oxidation catalyst device (DOC), a selective catalytic reduction device (SCR), and the like are available as exhaust gas treatment devices.
Particularly, the selective catalytic reduction device uses urea as a precursor of a reducing agent to reduce NOx (nitrogen oxide) contained in an exhaust gas and purify the exhaust gas. The reducing agent (aqueous urea solution) utilized in this exhaust gas treatment is supplied from a reducing agent tank to a reducing agent injection device through a reducing agent pipe. When the reducing agent remains in the reducing agent pipe after an engine is stopped, the reducing agent may be solidified in the pipe to cause clogging in the pipe.
Therefore, a process of collecting the reducing agent from the reducing agent pipe into the reducing agent tank (purge process) after stopping the engine is performed. In this purge process, the residual reducing agent in the reducing agent pipe as well as bubbles are collected into the reducing agent tank.
On the other hand, since the work vehicle is used under a harsh condition with much dust present, it is highly possible that impurities are entrained in the reducing agent tank, thus it is necessary to remove the impurities. A strainer is provided at a suction port for the reducing agent in the reducing agent tank to remove the impurities. A reducing agent tank provided with a filter as such a strainer at a suction port is disclosed in, for example, Japanese Patent Laying-Open No. 2011-137441.